Traditional telepresence implementations utilize multiple cameras for capturing all the participants in the near end conference room. Each camera captures only a portion of the conference room. Images captured by each camera are, typically, given to a codec for compression. The compressed images are transmitted to the far end conference room, where they are decompressed and displayed on one or more display screens. Because each near end camera captures only a portion of the near end conference room, the far end combines the images corresponding to each of the near end cameras by displaying the images on display screens placed adjacent to each other. The adjacently displayed images appear as a single seamless composite image to the far end participants.
Typically, multiple cameras are mounted on fixed camera mounts that point the cameras in a fixed direction. The orientation of the camera mounts is precisely arranged so that the images captured by each of the multiple cameras, when displayed on adjacent display screens at the far end, accurately align with each other. Therefore, when the far end combines the images received from the near end cameras, these images seamlessly combine to appear as a single image to the far end participants. However, over time, the orientation of the camera mounts can change due to vibrations, expansion/contraction of the mount components due to temperature changes, physical contact by conference participants, etc. A change in the orientation of a camera mount directly affects the orientation of the camera, which, in turn alters the portion of the conference room captured by that camera. Consequently, when the images from multiple cameras with altered orientation are combined at the far end, the seamlessness in the combined image can be lost.
For example, FIG. 1 shows four adjacently placed display screens 152, 154, 156, and 158 at a far end conference room 102 displaying images 104, 106, 108, and 110 received from four near end cameras (not shown). The effect of change in camera orientation can be seen at the boundaries of adjacent images. For example, boundary 112 between images 104 and 106 shows misalignment in display of objects that transition from images 104 to image 106. Similarly, misalignment can be seen at boundary 114 (between images 106 and 108) and at boundary 116 (between images 108 and 110). FIG. 2 shows a closer view of the misalignment between adjacent images 204 and 206 in composite image 202. Objects 208 and 210 in images 204 and 206, respectively, represent the same desk at the near end. However, they show up misaligned in the composite image. Misaligned objects, such as the ones shown in FIGS. 1 and 2, can be very distracting to far end conference participants viewing the composite image. The situation is even more bothersome when the boundary between two misaligned images passes over an image of a conference participant.
In addition to alignment, other camera parameters such as camera focus, lens settings, camera gain, noise levels, etc. may also differ between cameras over time. These differences in camera parameters manifest themselves as differences in color, contrast, brightness, etc. between adjacent images reproduced at the far end display screens. Thus, far end participant will not see a desired seamless composite image.